I think it's the formation. It is essentially removing an attacker or midfielder for an extra cb. The cbs are obviously not going to pass as well as a midfielder and will more often than not, hoof it up bypassing our midfield. It also makes our attack too dependent on our wingbacks, which we really don't have. Young and Valencia are the closest players that fit that role, but they can't dribble past players with a lot of success. They have no one to overlap them as they would if they were wingers.
Our midfield then becomes Rooney and Carrick. Rooney likes to pass the ball to the right wingback which again puts more pressure on the wingback to create. LVG also likes the wingers and wingbacks to keep the width, which then hampers players like Januzaj who has nobody to help him. This is why you see him wait on the wing and when he does get the ball has to either dribble past a player or cross it in. He can't exactly drift centrally. Shaw and Rafael also get hampered by this role because they aren't used to having the entire wing to themselves, and takes a way a key component to their game, their ability to overlap.
Switch to a back 4 and a 3 man midfield. It utilizes Shaw, Rafael, Di Maria, etc... much better.